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crossed the maximum permissible limit. In dry season the level of pollution was much high than in wet season. That indicates the water of Buriganga was not safe for drinking purposes, irrigation, fisheries, recreational activities and various industrial uses for most of the times of year.

In Bangladesh, the tannery solid wastes are converted to protein-concentrate to be used as poultry feed, fish feed, and in production of organic fertilizers. Over the last several years it is a common phenomenon in the largest tanning area of the country, the Hazaribagh tannery area at the south-east part of Dhaka city. One of the major concerns of these activities is the heavy metals, especially chromium, used in the tanning processes. A total of 18 samples were collected to study the heavy metal status of protein-concentrate production in the tanning area at various stages from the source to the final product, and to compare this with the imported ones. The various types of solid waste processing for protein-concentrate production were covered in sampling, and along with the heavy metal status these processes were studied comprehensively. The maximum chromium content of the solid waste was found to be 3.2 %. The final products sampled at two different places contained as high as 2.49 % and 1.94 % chromium. Cadmium, lead, arsenic, and mercury contents of all samples were also determined. The detected maximum and minimum concentrations of these elements were found to be: 3.888 ppm and 0.991 ppm for cadmium, 30.114 ppm and 7.577 ppm for lead, 2.212 ppm and 0.099 ppm for arsenic, and 13.916 ppm and 0.166 ppm for mercury.

In the north-eastern part of Dhaka the 'Turag River' extends over Ashulia thana with a few branches. The north-eastern part of Ashulia thana mainly constitute low lands with a physiography of Madhupur Tract interlaced with Brahmaputra Floodplain. Monsoon extends over these lands from May to October and from July to October these lands remain flooded with a water depth of more than 180 cm to less than 275 cm due to surface runoff of rain water and overflow of the river canals. The area under water during this four month period can be used for economic applications such as various types of fishery as well as enhancing the present recreational applications. For these purposes the physical, chemical, and biological aspects of the water are studied to evaluate its suitability for the applications. The study was held over the period of July through December, 2006, samples being taken once every month. The physical parameters covered transparency, odor, temperature, salinity, EC, TSS, and TDS. The chemical parameters of water studied were pH, DO, BOD 5 , COD, hardness, NO 2 ---N, NO 3 ---N, PO 4 3---P, SO 4 2---S, Cl-, Na, K, Ca, Fe, Ni, Cu, Zn, Cd, Pb, and Hg. Among the biological parameters 'phytoplankton' and 'zooplankton' were qualitatively identified in microscopic observation up to genera. From July to October the water was transparent and of good odor, temperature ranged from 28.2 O C to 24.6 O C, salinity within 0.58 to 0.83 mg/L, EC within 250 to 608 µ mho/cm, TSS 0.42 to 0.82 mg/L, and TDS within 2.8 to 5.2 mg/L. Among the chemical parameters, pH ranged from 6.6 to 7.4, DO within 6.4 to 6.9 mg/L, BOD5 within 1.5 to 3.28 mg/L, COD within 3.04 to 12.89 mg/L, hardness 26.08 to 37.5 mg/L, NO 2 --N from undetectable to maximum 0.562 mg/L, NO 3 --N within 0.539 to 2.158 mg/L, PO 4 3 --P 2.35 to 2.75 mg/L, SO 4 2 --S 0.23 to 0.29 mg/L, Cl-1.65 to 6.16 mg/L, Na 3.6 to 12.5 mg/L, K 9.7 to 11.5 mg/L, Ca 6.52 to 14.82 mg/L, Fe 0.1269 to 0.5062 mg/L, Ni 0.028 to 0.050 µg/L, Cu 0.028 to 0.043 mg/L, Zn 0.023 to 0.048 µg/L, Cd 0.0023 to 0.0043 µg/L, Pb 0.043 to 0.093 µg/L, and Hg was not detected at ppb level. Among the biological parameters a number of phytoplankton were identified covering the classes of Bacillariophyceae, Chlorophyceae, Euglenophyceae, and Cyanophyceae. The zooplanktons included the orders Cladocera and Copepoda within the class Crustacea of phylum Arthropoda.